The Treatment of Depression Collaborative Research Program (TDCRP) was the first multicenter, comparative clinical trial in the field of psychotherapy research initiated by NIMH. The study compared the efficacy of two psychotherapies, interpersonal psychotherapy (IPT) and cognitive behavior therapy (CBT), with imipramine plus clinical management (as a standard reference condition) and placebo plus clinical management (as a control condition) in the treatment of outpatients with nonbipolar, nonpsychotic, major depressive disorder. The proposed study will extend in important new directions the substantive results on the outcome of psychotherapy and pharmacotherapy for major depressive disorder that have emerged from the TDCRP. The new study will be conducted through a comprehensive series of data analyses and investigations of treatment process and will be implemented as a consortium among the three original research sites: the Departments of Psychiatry at the University of Pittsburgh, George Washington University, and the University of Oklahoma. The primary goals of the new consortium are (1) to examine further the efficacy of psychotherapy and pharmacotherapy in the treatment of depression and (2) to elucidate the mechanisms through which these therapies produce their effects, including treatment- specific factors, common or nonspecific factors, and factors related to negative effects (to the extent that they occurred). Data analyses will be organized around three specific themes: further analyses of treatment efficacy involving alternative measures of outcome not yet examined (e.g., measures of social adjustment, individualized measures of outcome, data collected from significant others); investigations of moderators of effectiveness that may have interacted with treatments to enhance or diminish efficacy (e.g., subtypes of major depressive disorder, personality styles and disorders, life stress, social supports); and examination of direct mediators of change during the treatment process (e.g., therapeutic alliance, tricyclic plasma levels in the imipramine condition). A final goal of the consortium will be to disseminate our findings to as broad an audience, both clinical and scientific, as possible. Also, through the mechanism of a U01 agreement, the research sites will continue, on a reduced scale, collaboration with NIMH on some data analyses and publications.